1. Field of the Invention
This invention relates generally to semiconductor devices and more particularly to a switch that has fast switching speed and high current capability.
2. Description of the Related Art
The metal-oxide-semiconductor field effect transistor (MOSFET) is the most widely used switching device in very large scale integration (VLSI) circuitry. Its popularity derives from its simple structure and low fabrication cost. The bipolar junction transistor (BJT) is another semiconductor device. The BJT is widely used in high power and high speed products. A MOSFET is typically turned on by applying a voltage to a gate to create a field effect channel, while a BJT typically is turned on by forward biasing a PN junction which renders the device conductive.
In some applications, it is desirable to have a device that is simple to fabricate and can conduct high current. Examples of such devices are: (1) a lateral double-diffused transistor (LDMOS), (2) a vertical double-diffused transistor (VDMOS), and (3) a V-groove double-diffused transistor. However, the fabrication of these devices is based on BJT processing. Thus, it is difficult to adopt these devices in conventional low-cost CMOS processes. As a result, they are not widely used in VLSI.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.